Engines such as those used to power automobiles and commercial vehicles typically are started by turning an ignition key. Turning the key causes a connection between a starter relay coil or solenoid switch and the positive terminal of a vehicle battery thereby energizing the coil and closing a contact on the relay. With the contact closed, the vehicle's starter motor is connected to the vehicle battery so as to crank the engine. In conventional starters, when the contact closes, it makes contact with a metal disc which completes a connection between the positive terminal of the battery and the primary terminal of an ignition coil. The engine is started in a conventional internal combustion engine by rotating a flywheel until the engine fires and is able to run on its own power, commonly referred to as cranking the engine. The flywheel typically is rotated by the starter motor, which is fed with current from the battery. After the motor starts, the ignition switch contact returns to its normal operating position, and the starter relay switch opens, thereby breaking contact with the disc.
Essentially, an automobile or commercial vehicle powered by a conventional internal combustion engine requires a starter that acts as a separate electric motor to rotate the engine crankshaft so as to start or crank the engine. Thus, to successfully start the engine, the starter must be able to rotate the crankshaft at a speed sufficient to fire-up the engine. The starter is electrically powered by the automobile battery, which also provides power to various vehicle devices such as the exterior and interior lights, the horn, temperature and fuel gauges, and a host of other accessory devices commonly found on the vehicle.
More generally, because the starter requires power to function, the vehicle requires a source of energy stored in a quantity sufficient to crank the engine while also providing power to other devices. In conventional systems, the power is supplied by the battery vehicle as already described. The battery also must power the vehicle's electrical system. The electrical systems of standard automobiles and commercial heavy-duty vehicles, at least since 1975, ordinarily have included an ever increasing number of various electronic control units (ECUs) of ever more complexity. Today, ECUs perform various critical functions on a vehicle. For example, injection of fuel into the combustion chamber on an internal combustion engine can be controlled by an ECU so that an electromagnetic injector pulses on-off so as to supply fuel quantities in a desired proportion to the air-intake. Similarly, ECUs are ordinarily used to control such electronic devices as door locks and outer mirrors on the vehicle. Of particular relevance in the context of the present invention, ECUs are frequently used to control the operation and sequencing of operations necessary for starting a vehicle.
The amount of power that must be supplied to power the electrical system as well as power the starter used to crank the engine is a function of the conditions under which the vehicle is operated. For example, during cold weather, the engine is more difficult to start thus requiring more energy to crank, and extra loads arise when devices such as the heater are left on while the engine is turned off. Thus, there is an ever prevalent need to provide the vehicle with a power supply that is both reliable and capable of providing power in a quantity sufficient to crank the vehicle engine under various operating conditions.
Power conventionally has been supplied in vehicles by standard lead storage batteries. A long-recognized limitation of lead storage batteries, however, is the batteries' inherent tendency toward relatively rapid depletion. Specifically, it has been estimated that such batteries possess an expected operation life of approximately one year. With continuous operation, moreover, the internal resistance of such a lead storage battery increases such that the battery's depletion occurs at an increasing rate over time.
Attempts have been made to provide more reliable sources of power for starting engines and powering electrical devices in vehicles. U.S. Pat. No. 5,146,095 to Tsuchiya et al., titled Low Discharge Capacitor Motor Starter System, for example, suggests supplementing the power supplied by a conventional vehicle battery by combining the battery with a high-density capacitor (also commonly referred to as a double-layer or molecular capacitor). Tsuchiya et al. requires that the capacitor be disconnected from the starter at all times save immediately prior to cranking the engine when the capacitor must be coupled to the starter in order to energize the starter for cranking. A more fundamental limitation of Tsuchiya et al., however, is that the battery nevertheless remains essential because, it is the battery that maintains the charge of the capacitor. Given the ever present need to maintain the charge on the capacitor in order to crank the engine, the useful life of a Tsuchiya et al. system remains substantially constrained by the useful life of the battery, as it is the battery that maintains the capacitor's charge.
Similarly, U.S. Pat. No. 5,207,194 to Clerici, titled System For Starting An Internal Combustion Engine For Motor Vehicles, suggests using a high-capacitance capacitor to supply power to the starter to crank a vehicle engine. Specifically, Clerici provides a set of switches that in a “second condition” connect the capacitor to the starter to power the starter when cranking the engine. In the “first condition,” however, the switches connect the capacitor to the battery so that the capacitor can be charged by the capacitor. Hence, like Tsuchiya et al., Clerici also requires an adequately charged battery in order to maintain the charge on the capacitor in order to crank the engine. Thus, as with Tsuchiya et al., the usefulness of the Clerici system is constrained by the need for a charged battery in order to sustain the battery.
U.S. Pat. No. 5,925,938 to Tamor, titled Electrical System For A Motor Vehicle, also suggests using a capacitor and battery device for cranking an engine and powering a vehicle electrical system. Tamor, though, seeks to overcome the limitations inherent in Tsuchiya et al. and Clerici, by charging the capacitor with the alternator and/or battery. Power delivery in Tamor is current-controlled by a resistor-and-diode device that limits current from the battery to the starter when the engine is being cranked and allows current from the alternator to the capacitor and battery when the engine is running. A limitation noted in Tamor itself, however, is that the capacitor store relatively little energy and that capacitor recharging occur only infrequently. This is necessitated by the need to reduce the electrical loss that occurs through the resistor of the current control whenever it is necessary to recharge the capacitor off the battery.
There is thus the need for a system that provides power rapidly and efficiently to a vehicle starter to crank the vehicle's engine, powers the electrical system of the vehicle, and yet is also reliably maintained for continuous use over a prolonged period for powering both the starter and the electrical system.